1. Technical Field
The present invention relates to an atomic oscillator.
2. Related Art
An atomic oscillator using transition energy of an atom as a reference frequency has been widely used in a communication base station or the like as one of oscillators having the highest accuracy. There are several types of atomic oscillators, and a microwave double resonance type atomic oscillator using a rubidium (Rb) lamp has been most generally used.
Recently, an atomic oscillator using a phenomenon referred to as coherent population trapping (CPT) which is one of quantum interference effects has been proposed (for example, refer to JP-A-2015-62167), and a reduction in the size of the atomic oscillator and a reduction in the power consumption are expected, compared to the related art. In a case of a CPT type atomic oscillator, a coherent light source such as laser is used in a light source, and high frequency signals are superimposed, and thus, the side band thereof is used in the exhibition of the CPT phenomenon. The CPT type atomic oscillator is an oscillator using an electromagnetically induced transparency (EIT) phenomenon in which absorption of coherent light stops in a case where an alkali metal atom is irradiated with coherent light rays having two types of different wavelengths (frequencies).
In order to exhibit the CPT phenomenon as the light source of the atomic oscillator, high accurate adjustment of an output wavelength of a laser element or the like is necessary. In a case where an injection current with respect to the laser element or the like is changed, it is possible to adjust the output wavelength.
However, in a case where the injection current with respect to the laser element is changed, a light output of the laser element or the like is simultaneously changed, and thus, it is necessary to form a control loop of the atomic oscillator in consideration of this circumstance, and complicated control is necessary.